Is there a negative bias on health information online?

[katieb]

It seems likely that the people who go online and post about their experiences with a particular drug or illness are not those who have had good experiences. It probably doesn't occur to people who get better immediately or have no side effects to post about their experiences, while those who are posting about it are probably having negative experiences. You can go online and for any given drug find a dozen bulletin boards of people describing their horrific experiences.

So, is there an inherent negative bias to health information online (particularly that provided by laypeople)? Might that affect the people searching for information by scaring them or even having them refuse treatment? How does this possible bias affect those seeking information, and does it encourage people to dwell on the negative aspects of their experiences?